According to the Denver Post, the report released Wednesday says 93 percent of cars already pass the tests and questions whether the program is needed for air quality.

The program that started in 1980 operates in nine Denver metro area and northern Front Range counties. Vehicles manufactured in the last four years are exempt from the program while earlier models must be tested annually or every other year.

The Department of Public Health and Environment that administers the program says more vehicles could be exempt from testing but says the program is useful in helping to lower ozone concentrations in the area, which is out of compliance with federal ozone standards.